NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 71, Issue 4
Displaying 1-26 of 26 articles from this issue
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Reviews
Review Paper
  • Norovirus contamination in oysters
    KIYOKUNI MUROGA, KEISUKE G. TAKAHASHI
    2005 Volume 71 Issue 4 Pages 535-541
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.535
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      The acute gastroenteritis caused by norovirus (Genus Norovirus of the Family Caliciviridae) is the most important non-bacterial gastroenteritis in the world, and this disease is often attributable to shellfish ingestion. Numerous studies have been made in various fields of science related to medicine and food/environmental hygiene, however, few investigations have been performed from the standpoints of shellfish biology and shellfish aquaculture in Japan. Based on reports on this problem made in various fields outside the fisheries science, this paper describes briefly the features of the disease and the causative agent previously called SRSV (small round-structured virus), transmission pathway involving shellfish ingestion, contamination of the virus in oysters, and two purification methods: depuration and relaying. Finally, the importance of studies on the virus-uptake mechanism of oysters and fate of the virus in oysters is discussed in order to establish a sanitary oyster aquaculture system and effective methods of depuration and relaying.
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Originals
  • A method to estimate carapace width of the red queen crab Chionoecetes japonicus using video images taken with a deep-sea video monitoring system on a towed sledge
    HIDEYUKI TAKAHASHI, TOSHIHIRO WATANABE, DAIJI KITAGAWA
    2005 Volume 71 Issue 4 Pages 542-548
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.542
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      Carapace widths of the red queen crab Chionoecetes japonicus were estimated using the video images taken with a deep-sea video monitoring system on a towed sledge (DVMSTS). A formula to convert the position on the video image to the real scale on the sea floor has been developed. The conversion was calibrated based on video images of a perspective grid recorded by DVMSTS in an experimental tank. In the in situ observation, the points of interest (left and right edges of a carapace) are above the sea floor and this causes an estimation error. By correcting the error, we obtained an accurate estimation of carapace width. The error ranged within ±10 mm when the sample was approximately within 500 mm from the sledge of DVMSTS.
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  • Trap catch of the red queen crab Chionoecetes japonicus when using conspecific crabs as trap bait
    TOSHIHIRO WATANABE, NAOTO HONDA
    2005 Volume 71 Issue 4 Pages 549-554
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.549
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      To investigate ghost fishing by lost traps for the red queen crab Chionoecetes japonicus, comparative fishing experiments with commercial traps were conducted in the sea area to the west of the Oki Islands in the Japan Sea. Catches with fish bait (mackerel) were compared both with catches from traps containing dead crabs (red queen crab) and without bait in 1992 and 1998. Male crabs were not caught by the traps containing dead crabs, but females were caught in small numbers. Unbaited traps caught a few crabs. Since dead decapods in traps can greatly reduce catches of conspecifics, catches with fish bait were compared with catches with fish bait plus dead crabs in 2001. Catches of male crabs decreased significantly in traps with fish bait plus dead crabs in all operations. Dead crabs repelled male crabs. On the other hand, females can escape from commercial traps by passing through the mesh because of their smaller size. Therefore, we think lost traps with dead crabs will not continue to attract new crabs. Since there were a few catches even in unbaited traps, however, we cannot exclude the possibility that the lost traps continue to catch crabs.
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  • Dietary value of marine rotifer Brachionus plicatilis at different population growth stages for larval Japanese flounder Paralichthys olivaceus
    TSUTOMU TOMODA, MASAHIKO KOISO, HIROSHI KUWADA, JAU-NENG CHEN, TOSHIO ...
    2005 Volume 71 Issue 4 Pages 555-562
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.555
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      This study assessed the dietary value of rotifers at different population growth stages for larvae of Japanese flounder (Paralichthys olivaceus). Rotifer cultures were prepared daily and continued for up to eight days. Rotifers were taken out on the 2nd, 4th and 8th day from the batch culture and equally enriched with freshwater Chlorella containing n-3 HUFA oil. The flounder larvae were reared in 500-L tanks for 16 days and supplied with different rotifers as above-mentioned. Population after 17-hr enrichment, which reflected their initial physiological status (low daily growth rate and egg rate), decreased in the 8th day rotifer. Feeding group moreover, the flounder larvae fed on those rotifers significantly showed the lowest growth and morphological development on the 16th day after hatching. Despite no marked difference in essential fatty acid (EFA) levels in rotifers among all groups, the EPA and n-3 HUFA contents in flounder larvae were significantly the lowest in the 8th day rotifer feeding group. These results show that the dietary value of rotifers was poor after the logarithmic growth phase of batch culture, in spite of enrichment with n-3 HUFA, similar to the results of larviculture of red seabream.
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  • Effects of Artemia nauplii density on survival, development and feeding of larvae of the horsehair crab Erimacrus isenbeckii (Crustacea, Decapoda, Brachyura) reared in the laboratory
    TADAO JINBO, KATSUYUKI HAMASAKI, MASAKAZU ASHIDATE
    2005 Volume 71 Issue 4 Pages 563-570
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.563
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      This study was conducted to examine the effects of prey (Artemia nauplii) density on survival, development and feeding of the horsehair crab Erimacrus isenbeckii larvae. Six levels of prey densities (0, 0.25, 0.5, 1, 2, 4 individual (ind.)/mL) were examined for their effects on survival, developmental period from hatching required to reach each larval stage, and growth of larvae. The number of prey consumed per larva per day was determined at five levels of prey densities (0.25, 0.5, 1, 2, 4 ind./mL) at the first, third and fifth zoeal stages. Survival rates increased with high prey density, and survival rates at the first crab stage were significantly higher at 2-4 ind./mL than at 0-0.5 ind./mL (P<0.05). The number of days required to reach each stage was lower as prey density levels increased, and was significantly lower at 2-4 ind./mL than at 0.25-1 ind./mL (P<0.05). Regarding growth, carapace length was longer as prey density levels increased, and carapace length at the megalopal stage was significantly longer at 2-4 ind./mL than at 0-0.5 ind./mL (P<0.05). The number of prey consumed by larvae tended to increase with high prey density; growth and zoeal feeding showed a tendency to be saturated when prey density level was 2 ind./mL. These results suggest that the optimal prey density for larval rearing of horsehair crab is at least 2 ind./mL.
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  • Target strength measurements on tethered live jellyfish Nemopilema nomurai
    MIYUKI HIROSE, TOHRU MUKAI, DOOJIN HWANG, KOHJI IIDA
    2005 Volume 71 Issue 4 Pages 571-577
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.571
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      The purpose of this study was to estimate the acoustic target strength (TS) of live Nomura's jellyfish Nemopilema nomurai found in the Yellow Sea and the Sea of Japan. The experiments were conducted at Yosu National University, Korea. Seven jellyfish were collected from coastal waters in southern Korea by SCUBA diving and from set-nets. Individual live jellyfish were suspended at the center of a seawater tank (5 m×5 m×5 m) tethered by thin fishing line, and their behavior was monitored by underwater cameras. The TS of each jellyfish was measured at 38 kHz (split-beam system) and 200 kHz (dual-beam system).
       The mean TS values ranged from -79.0 to -47.5 dB at 38 kHz and from -72.2 to -46.0 dB at 200 kHz, and tended to be higher at 200 kHz than at 38 kHz by 1.5 to 10.6 dB. The TS values of similar sized jellyfish were approximately 20 dB lower for those collected by SCUBA diving than those collected in the set-nets. The TS values also varied depending on the form change of the jellyfish.
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  • Cryopreservation of sperm of the endangered Itasenpara bitterling Acheilognathus longipinnis
    KAZUHIKO UEHARA, HIROMI OHTA
    2005 Volume 71 Issue 4 Pages 578-583
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.578
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      This study aimed to develop an effective method for the cryopreservation and artificial fertilization of cryopreserved spermatozoa of the endangered Itasenpara bitterling. Milt was mixed with a cryopreservation diluent (10% methanol plus 90% artificial seminal plasma for carp) and stood for 180 min; the percent motility of spermatozoa further diluted with buffered solution showed no significant change. Milt was diluted with the cryopreservation diluent (1:40), and each 80 μL of the dilution was dispensed into long capillary tubes. The tubes were cooled in liquid nitrogen (LN) vapor at various cooling rates to various temperatures and then immersed and stored in LN. The milt was thawed by immersing the tubes in water at 20°C for 7 seconds. Post-thaw motility was determined by the percentage of motile spermatozoa diluted with buffered solution. The tubes cooled at the rate of -14°C min-1 to -50°C and immediately immersed in LN demonstrated a significantly higher post-thaw motility (30.6±2.1%) than under other conditions. The post-thaw milt diluted 1:500 with tap water before insemination showed a high percentage of fertility (88.7%); however, the percentage decreased rapidly with high dilution ratios. In contrast, fresh milt showed an invariably high percentage of fertility regardless of the dilution ratio.
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  • Food habits of kichiji rockfish Sebastolobus macrochir in summer on the continental slope off the Pacific coast of Hokkaido, Japan
    TOSHIAKI OHMURA, TOMONORI HAMATSU, TOYOMI TAKAHASHI
    2005 Volume 71 Issue 4 Pages 584-593
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.584
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      The food habits of kichiji rockfish Sebastolobus macrochir were studied off the Pacific coast of Hokkaido. Fish samples were collected with a bottom trawl net at depths of 300-1,000 m in the daytime in July 2001 and 2002. Benthic invertebrates were collected with a Smith-McIntyre grab and a sledge net in July-August 2002. The percentage of empty stomachs of S. macrochir was low particularly in fish ≤150 mm SL, indicating active feeding during the summer. Dietary analysis was conducted using 897 fish (43-271 mm SL). The principal prey item changed from small crustaceans such as gammarids and cumaceans to crustacean decapods and ophiuroids (chiefly Ophiura leptoctenia) with increase of fish length. Ophiuroids, which are probably the most abundant prey in this study area, became very important in the diets of S. macrochir with the growth of fish. In addition, ophiuroid feeders including S. macrochir are very low in biomass in this study area. Such a foraging strategy of S. macrochir seems to reduce the intra- and inter-specific competition for food.
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  • Comparison of feeding conditions in adult marbled rockfish Sebastiscus marmoratus between an inclined sea wall of Kansai International Airport and a natural rocky shore
    TAKAYUKI KUSAKABE, HIROYUKI ARIYAMA, HIROAKI OHMI, TAMAO AMANO
    2005 Volume 71 Issue 4 Pages 594-600
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.594
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      In order to evaluate the capacity of the inclined sea wall of Kansai International Airport island as a nursery ground of marine organisms, we examined feeding conditions of adult marbled rockfish Sebastiscus marmoratus caught from a rubble mound type inclined sea wall of the airport and a natural rocky shore near the southern mouth of Osaka Bay. We also compared fauna and abundance of macrobenthos between the two habitats. Sebastiscus marmoratus caught from the sea wall took less food than those from the natural shore. Amphipods accounted for a high percentage of its food items instead of decapods, which are ordinarily the principal food organisms of adult S. marmoratus. On the other hand, the fauna, weight, and number of macrobenthos on the sea wall were generally less than those on the natural shore. Particularly, the number of decapods was about one third of that on the natural shore. These facts indicated that there is a shortage of the food preferred by S. marmoratus on the sea wall of Kansai Airport. We also discuss the relationship between these feeding conditions and the shape of the sea wall of the airport.
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  • Relationships between individual density and territory size in juvenile red sea bream in natural waters
    FUMIHIKO ABE, KOSAKU YAMAOKA
    2005 Volume 71 Issue 4 Pages 601-610
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.601
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      We observed the territory of juvenile red sea bream Pagrus major to detect the relationships between density and territory size at Morode Cove in Ehime Prefecture from January 2001 to October 2003 using SCUBA. The density of juveniles showed the highest value in 2001 (0.201 individuals/m2), the lowest one in 2002 (0.051 individuals/m2) and the intermediate one in 2003 (0.096 individuals/m2). The growth in 2001 was slower than that in both 2002 and 2003. We confirmed 131 territories of individually identified fish during the 3 years, and some territories were maintained for a long period. At the time of high density in 2001, the mean value of the territory sizes in each size class increased up to 8 cm size class, but did not show any clear increase thereafter and became nearly constant at c. 6.4 m2. At the time of intermediate density found in 2003, that value increased up to 9 cm size class, but became nearly constant thereafter at the level of c. 15 m2. At the time of low density found in 2002, that value increased with growth and became c. 50 m2 at the stage of 14 cm size class. These results suggest that the territory size of juvenile red sea bream is clearly correlated with the individual density, and the size became smaller at the time of high density and vice versa.
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  • Improvement of “kurozukuri ika-shiokara” (fermented squid meat with ink) odor with Staphylococcus nepalensis isolated from the fish sauce mush of frigate mackerel Auxis rochei
    YASUHIRO FUNATSU, KATSUYA FUKAMI, HIDEHIRO KONDO, SHUGO WATABE
    2005 Volume 71 Issue 4 Pages 611-617
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.611
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      The Staphylococcus nepalensis strain, which was isolated from frigate mackerel fish-sauce mush added with soy sauce koji, was inoculated into “kurozukuri ika-shiokara” (“kurozukuri”), fermented squid meat with salt, liver and ink traditionally produced in Toyama Prefecture, to improve its odor. Extractive components and volatile components of “kurozukuri” after incubation at 4°C for 30 days with the cultured bacterium were examined by HPLC and GC/MS analyses. There was no difference in the contents of extractive components between bacteria-treated “kurozukuri” and non-treated one. However, the contents of volatile components, acids, aldehydes, sulfur-containing compounds, alcohols and esters, in the former were different from those in the latter, and dimethyl disulfide, which existed in the latter, did not detected in the former. Sensory evaluation revealed that fishy odor and disagreeable squid odor notes of the former treated with the bacterium were weaker than those of the latter.
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  • Effect of salting of salmon on the chemical and microbiological characteristics of salmon Izushi
    MASANORI SASAKI, YUJI KAWAI, MAMORU YOSHIMIZU, HARUO SHINANO
    2005 Volume 71 Issue 4 Pages 618-627
    Published: 2005
    Released on J-STAGE: August 24, 2005
    DOIhttps://doi.org/10.2331/suisan.71.618
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      Izushi was prepared from raw and salted chum salmon (Oncorhynchus keta) fillets. Effects of salting on the chemical and microbiological characteristics during pre-treatment and the ripening process were investigated to compare these Izushi products. Both reached an acceptable state by ripening for 36 d. During the ripening process, pH values of both Izushi samples remained below pH 5.2 and organic acids in Izushi were mostly acetic acid used as vinegar. By the salting and soaking processes, lower molecular compounds were eluted away and salting decreased microbial counts in Izushi products. In Izushi prepared from salted fish, free amino acids were increased while the increase of VB-N was suppressed during the ripening process, and the fish meat in the ripened product had a more fragile texture. The salting of fish fillets was suggested not to affect microbial flora of Izushi. Regardless of the salting, microbial counts of Izushi did not significantly increase during the ripening process, and after ripening for 36 d or longer, Leuconostoc mesenteroides subsp. cremoris and Saccharomyces cerevisiae became dominant as the groups of lactic acid bacteria and yeasts, respectively.
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